I have a have my sump running down into about 20lbs of rubble. through a bubble trap to my fuge with a 5 or six inch sand bed with some more rubble and LR and Macro. then through to a mechanical filtration area with a skimmer heaters, uv sterlizer and the return. I am not well emersed to say what it would take to go skimmerless. I use i skimmer cause I run a pretty dirty tank feed often.

Deep sand bed is considered anything around four to six inches. Anything less is wont offer the same effect and anything more can cause harmful gas build up of decaying matter in the sand. Its helps with denitrification. The bigger the foot print will just offer more room for additional beneficial organisms to grow.

Rubble is just a natural way to do the same thing as bioballs. I use rubble cause I can't run a wet/dry setup. It has to all be wet and bioballs lose significant effectiveness if they are completely submerged where as rubble does better as such. Plus it houses beneficial organisms and food like copepods, amphipods and such, not just bacteria like bioballs.

I have a couple different Macros in my sump. I have chaeto, culerpa, dragons breath and some red macro i forget the name at the moment. I use to vary my tangs diet off of these. But everyone has tehre opinion on which is the best and offers beneficials properties. I'm not that technical on macro's. Just don't use Mangroves.

A bubble trap is dividers between sections that help remove bubbles befor they reach your return pump to be pumped bak into your main display. Added a pic with a generic bubble trap design. Some people get more elaborate. Basically just water flow areas that go down then up to give ampl opportunity for bubbles to be lifted out before carrying on.bubble trap.jpg